3. Nest (National Employment Service and Training) is a leading
training institute for ASNT level II. We are the only training centre
giving 100% placement assistance to the candidates till candidates
get placed. Our trainers are having more than ten years of field
experience in industries like petroleum refineries and power plant
(nuclear, thermal). The candidates will get both theoretical and
practical during the training session. We are moulding our
candidates with advance training medium like visual and audio to
enrich their knowledge. Our candidates will get a globally
authentication certificates from ASNT America Society for Non
Destructive Testing level II as per SNT-TC-1A standard on
successful completion of training and practical exams.
Our candidates will get onsite training in the particular industries
like refineries and power plant to get a real time experience. Nest
takes whole responsibilities of our candidates developing in their
career. Other than NDT training, we are providing Motivation class,
personality development session to get through in their interviews
with fear.
4. Vision:
Nest Institute of NDT posse’s high quality
international standard training for NDT in
accordance with quality management system and
pursuing placement for candidates to improve their
career.
Our Mission:
To give quality training and education along with
placement for the youngsters to enrich their career
(or) to make their life delightful.
5. The earliest and most useful method of NDT is
visual examination. Important details can be collected
during VT which would be useful for future analysis
and also to decide on the types of NDT to be used for
as further analysis. Also, VT should be carried out as
a complementary method to all other NDT methods.
VT should proceed and succeed all other
examinations. Inaccessible areas can be inspected by
means of boroscope and fiber-optic techniques.
Depending upon the severity of the surface defect
and the component in use, decision will be taken for
salvaging the component or not. If the product is
found unacceptable during visual examination itself,
further NDT need not be carried out, thus saving
time and cost of inspection
6. Surface deposits
Scaling
Corrosion
Discoloration
Oxidation bulging
Missing parts
Mechanical damage
Dimensional conformance
Gross effects visible on the surface
Distortion of components during fabrication and in
services
General corrosion on the surface of a component
7. Liquid penetrant testing (LPT) is another means of enhancing the
capability of visual examination. It is suitable for use on smooth
surfaces of all materials, magnetic as well as non-magnetic. It is
limited to surface defects. Its inability to indicate the depth or
breadth of flaw should be kept in mind while selecting this
method for particular application.
Use of LPT for porous materials is ruled out since the absorption
into the pores would mask the presence of defects. A clean surface
is a pre-resist as penetrant cannot enter in to the cracks that are
filled with dirt, oil, or other matter.
Size, shape, weight and number of workpieces to be inspected
often influence the selection of a penetrant system. The desired
degree of sensitivity and the cost are the most important factors in
selecting a system.
LPT can also be used for leak testing. In this case, the component
casting is filled with penetrant and developer is applied outside
the surface.
8. LPT is selected for detecting the following types of
discontinuities on the surface of a component.
Cracks of any orientation
Porosity
Pin holes
Voids
Forging laps
Forging bursts
Lamination in plates
Various types of weld defects
Corrosion cracks
Creep fissures
Fatigue cracks
9. While LPT is effective only for fine surface discontinuities, the need
remains to detect larger surface flaws or those present just below the
surface. The need is met by magnetic particle testing (MPT). This
technique is applicable only for ferromagnetic materials. MPT is a
considered more sensitive than LPT. MPT requires a higher degree or
operator expertise to ensure that the magnetic fields are aligned in the
correct direction in order to detect the defect. Flaws oriented
perpendicular to the induced magnetic field is only reliably detectable.
Hence the challenge is to induce magnetic field lines in a given work piece
so that they are most likely to be perpendicular to the flaw orientation.
Therefore, prior knowledge on flaw orientation and or introduction of
magnetic fields in several directions are is essential.
It is commonly agreed that defects breaking the surface are most severe
amongst the various discontinuities occurring in components. For
dynamically loaded structures, their removal is essential. Their detection
in ferrite materials is most easily accomplished by MPT. Since the depth
determination of the surface breaking cracks is almost impossible, crack
depth measurements may be additionally employed to asses them.
Detection of subsurface defects by MPT is impossible if the components
are thin, but generally it requires ideal testing conditions.
10. MPT is used for detecting following discontinuities in ferromagnetic
materials.
Surface discontinuities:
Cracks and tears
Porosity
Shrinking cavities
Slag inclusions
Voids
Forging laps
Grinding cracks
Corrosion cracks
Fatigue cracks
Discontinuities just below the surface (within around 6mm depth from
the surface sensitivity goes down as a defect is deeper):
Larger size cracks in various orientations
Pores
Slag inclusions
11. The other NDT methods are used for detection of defects
which are open to the surface nearer to the surface. To
detect more deeply seated discontinuities, NDT methods
with test medium capable of deeper penetration and
system that senses even minute changes in the
characteristics, behaviour of the test medium is required.
Radiographic inspection is one of the most widely used
methods of NDT as this is applied to all metals and
alloys, both ferrous and nonferrous, for detection of
volumetric type of defects. The range of capabilities
offered by the variety of sources and equipments has
brought radiography to the forefront of NDT techniques.
Testing of multilayer vessels and welds is generally a
difficult task due to in accessible inner layers. RT is the
only NDT method to evaluate multilayered vessels
during manufacturing stages and inservice.
12. Development of micro focal X-ray units has made it possible
to extend radiographic practice to meet the requirements of
more stringent quality levels demanded for critical
applications, besides a host of new applications. It is know
that the sensitivity in radiography depends to a large extend
on the focal spot size. In micro focal radiography, the focal
spot size is less than 100microns and typically 15-50 micron
as compared to a few mm or ½ a mm in conventional
radiography. Using microfocal RT, intricate geometrical
components such as tube to tube sheet. Welds can be tested
with a sensitivity of even 1% of wall thickness 0-3mm.
microfocal RT can be used for detection of micro cracks of
around 25micron in size. Another application of microfocal
RT is to check the integrity of micro-welds used electronic
integrated circuits.
One of the advantages of RT is that no prior preparation of
the surface of the component is necessary. The main
disadvantage of the RT is the possible hazards due to
exposure to radiation if proper care is not taken.
13. RT is selected to detect and size the following types of
discontinuities
Cracks (parallel to the radiation beam)
Volumetric defects such as slag inclusions, voids etc:
Porosity
Blockages or deposits inside the pipe lines are
pressure vessels
Material thickness
To detect hidden foreign material inside a component
14. Ultrasonic testing involves use of high frequency sound waves
coupled to the components to be inspected and studying the
reflection pattern of these waves. UT is finding increased
applications in various industries. Several wave modes such as
longitudinal, shear and surface waves can be used depending
on the orientation and location of the discontinuities. Different
techniques such as pulse-echo, through transmission, and
pitch-catch or employed. The advantages of UT are real time
availability of results, higher penetrating power of these
waves, higher sensitivity for planner defects, independence
sensitivity over depths, low cost for inspection, higher
portability to the equipment and compatibility for automation.
But the subjectivity of the results on the operators training and
skill is stumbling block for its wider acceptance. With the
advent of microprocessors and automation, operator
dependability is being eliminated to a larger extent and UT
finding increased applications in industries such as power,
railways, chemical, aerospace etc:
15. UT of cast metals and alloys is renderd difficult due to
the influence of casting intricacy, micro structural
variations and surface roughness. Defects occurring in
the cast structure have irregular surfaces which scatter
the aquostic waves and makes UT more difficult. Hence
successful use of UT for inspection of castings depends
greatly upon the skill and expertise of the operator.
UT is the most suitable method of NDT for inservice
inspection (ISI) of components in power plants, chemical
process industries, etc:. Many times, RT cannot be
applied for ISI due to the requirements of two side
accessibility. UT is more sensitive flaw growth
monitoring has compared with RT in view of all these
advantages; the first choice of ISI is UT for volumetric
defects in components except for heat exchangers and
condensers where ECT is preferred.
16. UT Is Selected To Detect The Size The Following Type
Of Discontinuities
Surface breaking and hidden cracks in any orientation
Inter granular cracks
Laps
Laminations
Volumetric defects such slag inclusions, voids, ect
Porosity
Wall thickness measurements
Creep
Hydrogen encriptment
Liquid level measurement
To detect blockages, deposits, etc. in the pipe lines and
pressure vessels
